Evaluation of Face Stability for Mega Tunnel Under Varying Ground Strength Parameters

Abstract Transportation demands in developing countries necessitate the use of underground infrastructure, notably tunnels, which also serve as storage spaces for vehicles and military equipment, expanding their utility. Mega Tunnels, defined as those with a diameter exceeding 10m, offer diverse functionalities, including facilitating the storage and movement of large equipment and establishing comprehensive operational systems for urban areas. However, ensuring the stability of these tunnels’ faces poses a significant challenge due to their larger diameter, making it a crucial research focus. This study investigates the impact of various geological strength variables, such as Young’s modulus and coefficient of lateral earth pressure, on Mega Tunnel face stability. Employing the numerical analysis-based computational tool Midas Gts Nx, three-dimensional modelling was conducted to analyze Mega Tunnels. A parametric study involving approximately 40 models was undertaken, focusing on key locations including the crown, invert, and vertical sidewalls. Variable parameters such as critical cover-to-diameter ratio (C/D), Young’s modulus, and coefficient of lateral earth pressure were examined. The findings highlight the significant influence of geological strength characteristics on tunnel face stability prediction. This research offers valuable insights for the planning and design of Mega Tunnels in urban areas during the preplanning phase, enhancing their efficiency and effectiveness.